Liquid carrying vessels to facilitate the discharge therefrom of the liquid



Jan. 4, 1986 c. H. CARSLAW 3,227,331

LIQUID CARRYING VESSELS To FACILITATE THE DISCHARGE THEREFROM OF THE LIQUID Filed July 20, 1964 United States Patent LIQUID CARRYING VESSELS T0 FACILITATE THE DISCHARGE THEREFROM OF THE LIQUID Charles H. Carslaw, Yoker, Glasgow, Scotland, assignor to Drysdale & Company Limited, Yoker, Glasgow, Scotland, a corporation of Great Britain and Northern Ireland Filed July 20,1964, Ser. No. 383,644 Claims priority, application Great Britain, Aug. 7, 1963, 31,079/ 63 3 Claims. (Cl. 222 -464) This invention is concerned with improvements relating to liquid carrying vessels to facilitate the discharge therefrom of the liquid. In particular the invention relates to marine tankers of the type used for the transportation of crude petroleum oil.

The oil tanks of such a vessel have upstanding longitudinally and transversely disposed members attached to the base of the tanks for strengthening the structure of the vessel, the former comprising spaced, parallel longitudinal frames and the latter comprising spaced, parallel athwartship frames and bulk heads.

The hitherto known method of discharging the oil from each tank is to position one end of a suction pipe, the other end of which is connected to the suction in let of a pump which serves to discharge the oil, within one of the spaces defined by the lattice of longitudinal and transverse members and as near to the base of the tank as possible, limber holes being provided in the longitudinal and transverse members to permit the oil to flow, under gravity, to said one of the spaces from the remainder of the spaces as the oil is discharged from the tank.

To ensure economic operation of marine oil tankers it is essential that the time spent by the vessel in port while unloading be reduced to a minimum so that pumps are normally used which have a high flow capacity. In the hitherto known method, however, it has in practice been found necessary to reduce the rate of pumping, with a consequent increase in the discharge time, when the oil level in the tank falls to approximately 6-8 feet since the high suction developed at the maximum pumping rate induces vortices which cause air to be drawn into the suction pipe thereby air locking the pump when the oil falls below the above-mentioned level.

The primary object of the present invention is substantially to overcome the above disadvantage and to ensure that the discharge time may be reduced to a minimum in a simple and inexpensive manner.

In a liquid carrying vessel, of the type referred to, according to the invention a plate is located over the, or each, of the plurality of spaces, defined by the lattice like structure of longitudinal and transverse members, in which the end of the suction pipe remote from the pump is operatively positioned, whereby to cover, but not to enclose, said space, the end portion of the suction pipe remote from the pump being disposed through or adjacent to, the plate with the associated end of the suction pipe situated adjacent to the base of the tank.

In order that the invention may be more easily understood and more readily carried into effect the same will now be described more fully with reference to the accompanying drawing in which FIG. 1 is a vertically sectioned view of one of the plurality of spaces, defined by the lattice like structure of longitudinal and transverse members in a liquid carrying vessel, of the type referred to, according to. the invention, and

FIG. 2 is a plan view in the direction of the arrow A of FIG. 1.

Referring to the drawing, 1, 1 denote two parallel, spaced longitudinal frames, 2 denotes a bulk head dis- 3,227,331 Patented Jan. 4, 1966 posed transversely of the vessel and therefore at right angles to the longitudinal frames 1,1 and 3 denotes an athwartship frame disposed parallel to and spaced from the bulk head 2. These longitudinally and transversely disposed members present a lattice-like structure defining a plurality of spaces. The base of the tank is denoted by the numeral 4. Limber holes 5 are formed in the frame 1. Like limber holes (not shown) are also formed in the frames 1, 3 and in the bulk head 2.

An anti-vortex plate 6 spaced from and disposed substantially parallel to the base 4 of the tank is secured, as by the bolts 7, to the frames 1, 1' the plate 6 serving to cover, but not enclose a portion of the space defined by the frames 1, 1', 2, the bulk head 3 and the base 4 of the tank. The two opposed edge portions 8 of the plate 6 between the frames 1, 1 are downwardly directed as shown particularly in FIG. 1.

The plate 6 is centrally formed with an aperture 9 through Which is disposed the end portion of a suction pipe 10, the opposite end of which is connected to the suction inlet of a pump (not shown), the end of the suction pipe 10 remote from the pump being outwardly belled at 11 (FIG. 1) and being located the minimum distance from the base 4 of the tank which permits the free flow, of liquid to be discharged from the tank, to the interior of the pipe 10.

A fixed anti-spin plate 12 is disposed, between the plate 6 and the base 4 of the tank, substantially vertically i.e. in a plane substantially at right angles to the plate 6. The plate 12 is attached, as by welding, to the plate 6 but is preferably not attached to the base 4 of the tank.

The plate 6 serves substantially to prevent the development of vortices with consequent air locking of the pump by considerably increasing the path to the suction pipe 10 of any air vortex which develops so that the pump may operate at maximum capacity until the level of oil in the tank falls to the level of the upper edges 13 of the frames 1, 1 which are generally of the order of 18 in height from the base 4 of the tank. The plate 12 also serves to prevent the development of induced vorticity within said space.

The rate of pumping will generally have to be reduced for discharging the remainder of the oil, below the level of the upper edges 13 of the frames 1, 1, but, as will be appreciated, the relatively small volume of oil, in comparison with the corresponding volume in the hitherto known method, which is discharged while the pump is -operated at the reduced flow rate represents a considerable saving in the time required for discharging the tank, while by providing additional strengthening members (not shown) on the frames 1, 1 2 and the bulk head 3 the cross'sectional areas of the liinber holes 5 may be increased thereby facilitating the gravity flow of the oil to said space, in which the end of the suction pipe 10 remote from the pump is located.

The present invention has the advantages that no moving parts are involved and the plates 6, 12 may readily be removed when, for example, it is desired to paint the interior of the tank.

What is claimed is:

1. A liquid carrying vessel of the type incorporating liquid-carrying tank means having longitudinally and transversely dispose-d members attached to the base of said tank means, in which said longitudinally and transversely disposed members present a lattice-like structure defining a plurality of spaces, a plate located over each of said plurality of spaces, whereby to cover, but not to enclose, said space, a suction pipe disposed in association with said space, the suction inlet of a pump being connected to one end of said pipe and the other end of said pipe being disposed within said space, the end portion of said pipe which presents said other end thereof being disposed in close physical relationship to said plate With said other end of said pipe located adjacent to the base of said tank means, and an anti-spin plate disposed substantially vertically between the first-mentioned plate and the base of said tank means.

2. Apparatus as set forth in claim 1 wherein said antispin plate is attached to said first-mentioned plate but is not attached to the base of said tank means.

3. In a liquid carrying vessel of the type incorporating liquid-carrying tank means, longitudinally and transversely disposed members attached to the base of said tank means and forming a lattice-like structure defining a plurality of spaces, a plate located over at least one of said plurality of spaces to partially cover the one space, a suction pipe having its suction inlet disposed within the one space and adjacent the base of said tank means, and means disposed in said one space beneath said plate for minimizing spin in the liquid as it passes to said suction inlet.

References Cited by the Examiner UNITED STATES PATENTS LOUIS I. DEMBO, Primary Examiner.

HADD S. LANE, Examiner. 

3. IN A LIQUID CARRYING VESSEL OF THE TYPE INCORPORATING LIQUID-CARRYING TANK MEANS, LONGITUDINALLY AND TRANSVERSELY DISPOSED MEMBERS ATTACHED TO THE BASE OF SAID TANK MEANS AND FORMING A LATTICE-LIKE STRUCTURE DEFINING A PLURALITY OF SPACES, A PLATE LOCATED OVER AT LEAST ONE OF SAID PLURALITY OF SPACES TO PARTIALLY COVER THE ONE SPACE, A SUCTION PIPE HAVING ITS SUCTION INLET DISPOSED WITHIN THE ONE SPACE AND ADJACENT THE BASE OF SAID TANK MEANS, AND MEANS DISPOSED IN SAID ONE SPACE BENEATH SAID PLATE FOR MINIMIZING SPIN IN THE LIQUID AS IT PASSES TO SAID SUCTION INLET. 